Halinchondrin analogs have been disclosed as having anti-cancer and antimitotic activity (U.S. Pat. No. 6,214,865, incorporated herein by reference). In particular, Halichondrin B has been reported as a potent anticancer agent that was first isolated from the marine sponge Halichondria okadai (U.S. Pat. No. 6,214,865; WO 2005/118565 A1 and WO 2009/124237 A1, all incorporated herein by reference).

2,5-disubstituted (2S,5S)-3-methylene-tetrahydrofurans, such as the compound of formula 7a, can be an important building block for the synthesis of the halichondrin natural products and derivatives, as described in U.S. Pat. Nos. 6,214,865 and 5,436,238, and incorporated herein by reference.
wherein Piv is (CH3)3C—C(═O)—.
The synthesis of compounds, similar to the compound of formula 7a, has been described by Kishi (Pure Appl. Chem. 2003, 75, 1-17; J. Am. Chem. Soc. 2009, 131, 15642-15646; J. Am. Chem. Soc. 2009, 131, 15636-15641), Phillips (Angew. Chem., Int. Ed. 2009, 48, 2346) and Burke (Org. Lett. 2002, 4, 3411-3414, J. Org. Chem. 2003, 68, 1150-1153), all incorporated herein by reference. However, these methods can be undesirable for commercial manufacturing. For example, all these routes rely on asymmetric reactions that, despite their high degree of selectivity, can give rise to epimers, which are of particular concern in cases where the intended use of the molecule is in the manufacture of an active pharmaceutical ingredient. Furthermore, many of these asymmetric reactions employ chiral ligands that are not necessarily easily commercially available, and which can be a hindrance for large scale production.
There is a need in the art for a process for preparation of 3-((2S,5S)-4-methylene-5-(3-oxopropyl)tetrahydrofuran-2-yl)propanol (7a), and its analogs (7), that can be used in the preparation of halichondrin natural products, its derivatives and analogs, such as, for example and without limitation, eribulin, the compounds described in recent publication of S. Narayan and others (Bioorganic and Medicinal Chemistry letters, 2011, 1630-1633; Bioorganic and Medicinal Chemistry letters, 2011, 1634-1638, Bioorganic and Medicinal Chemistry letters, 2011, 1639-1643), and other eribulin analogs with modified side chains on position C32 of eribulin. In addition, there is a need in the art for a process for preparation of 3-((2S,5S)-4-methylene-5-(3-oxopropyl)tetrahydrofuran-2-yl)prop-1-yl pivaloate (7a), and its analogs (7), that can be prepared from commercially available starting material. Moreover, there is a need in the art for a process for the preparation of 3-((2S,5S)-4-methylene-5-(3-oxopropyl)tetrahydrofuran-2-yl)prop-1-yl pivaloate (7a), and its analogs (7), that can avoid the use of asymmetric reactions, including chiral ligands. In addition, there is a need in the art for a process for preparation of 3-((2S,5S)-4-methylene-5-(3-oxopropyl)tetrahydrofuran-2-yl)prop-1-yl pivaloate (7a), and its analogs (7), where the process is scalable and can lead to a product having high stereochemical purity.
